I need advice for my 1991 900 Convertible. The issue is the top mechanism in relation to the glass window during opening and closing. The window seems to "catch" and then pops down or up. During a recent event, where there were two other 900 convertible to compare with, we noticed that the back cross piece has lost its "bow" or arc. Any ideas how to proceed? can it be pushed back up (bent) to make it bow again, can I just replace the back cross piece (bow), what options do you suggest. We also observed that the glass seems to push up against the bow during the opening and closing operation. I'll add that I don't have the history of the car, I bought it in July and have very little info about the car. It appears to me that it is the metal bow that is "flattened" (observed from the outside), and looking at parts lists online, I think that is Bow #3!? or is it bow #3 AND 4 that are "flattened" is that possible? Can i get new (used) bows and are they easy to install (understanding the canvas top would have to be lifted first)? Aside from this issue, the top opens and closes and is positioned normally. In the photo of 3 900s, mine is the one on the left?